Writing the differential equation

A chemical reaction A -> B is carried out in a closed vessel. If the tank volume is 30.5 gallons, and there is now B in the tank at t=0, how much B in grams does the tank contain after 2 hours? The reaction rate is constant, k, and k= 9.3x10^-3 g/L per minute

2. Relevant equations

B = amount of B in grams, in the vessel at a given time, t (in hours)
dB/dt = inflow of B - outflow of B

3. The attempt at a solution

1. There is now outflow of B because the vessel is closed and the reaction only goes one way, so dB/dt = inflow of B